need insight about vortec misfire asap

[Southern Pride]

Thanks alot buds. I'm going to direct him to this post so he can see all this and relay exactly what he has and has not done.

 

[nine4gmc]

my neighbor has a 96 1500 and got a po300, po172 and po155. the printout said it was bank 2, sensor 1 so he changed the passenger side o2 sensor near the manifold, cap, rotor, wires and plugs(ac delco) and it did not go away. is there anything else he should try?

 

[Hezsus]

my neighbor has a 96 1500 and got a po300, po172 and po155. the printout said it was bank 2, sensor 1 so he changed the passenger side o2 sensor near the manifold, cap, rotor, wires and plugs(ac delco) and it did not go away. is there anything else he should try?

Read Aloicious's Post a few back.

 

[BURBAN GUY]

Also check the fuel pressure regulator and fuel spider. These are prown to problems.

 

[squeaky3]

check for intake leaks, buddy of mine had one hell of a time tracking down a random missfire, replaced every part of the fuel and spark system and still no go, replaced intake gaskets and it went away

 

[Hezsus]

i'm gonna have to look into some of these things, My misfire isnt enough to throw a code but you can feel the stumble at idle. mabye i'll get lucky and fix it when I tighten them noisy rockers

 

[notfastenuff]

I am going thru this now. First thing he needs to do is a compression check on all cylinders. That will eliminate a head/cylinder problem. If compression is good, I'd look into replacing the fuel injection spider. If his cap and rotor are good, that's about all that's left. My problem wound up being a burned valve. EXACT same problem you're stating.

 

[Aloicious]

that spider is super expensive to just replace, make sure you're checking the fuel pressure, even pulling the upper manifold to see if you can find evidence of fuel puddling or leaking from the regulator before throwing money at it....

glad you found the miss problem notfastenough, another known P0300 issue with the vortecs is the distributor gear gets worn, and knife edged, which causes extra play in the rotor and can cause the P0300 even with a new cap/rotor setup. just info for others looking for help on the problem. I hate P0300's they're so elusive sometimes...

 

[TruckinAin4Sissies]

If you're not replacing the whole distributor like I did (MSD Streetfire) then at least replace the dive gear with this;
GM Performance
Part Number: 10456413 It's an updated part.

 

[Aloicious]

yeah, the aluminum body vortec distributors is the only thing I'd replace the stock one with, why they used a plastic body is beyond me....I have an accel one (the only thing accel makes that I like), but I've heard good things about the e-bay ones too, and they're a lot less expensive.